1. Field of the Invention
The present invention generally relates to an image capturing apparatus, control method thereof, and program and, more particularly, to an image capturing apparatus having a function of removing alien substances adhering to a surface of an optical member, a control method thereof, and a program.
2. Description of the Related Art
Conventionally, an image capturing apparatus comprising an image capturing unit to execute photography and a photographic lens detachable from its main body has been known. In such an image capturing apparatus, when a photographic lens is detached, alien substances such as dirt or dust can readily adhere to the surface of an image capturing unit accommodated in the image capturing apparatus. When an alien substance adheres to the surface of the image capturing unit, a black shadow appears in a captured image, resulting in a partially defective object image. This leads to degradation in image quality of the captured image. To remove the alien substances adhering to the surface of the image capturing unit, users have to clean the surface of the image capturing unit.
In recent years, an image capturing apparatus having an alien substance removing function is also known. This alien substance removing function works by vibrating the member of the surface of an image capturing unit to automatically remove alien substances adhering to the image capturing unit. Japanese Patent Application Laid-Open No. 2002-204379 discloses an example of an image capturing apparatus having such an alien substance removing function. In this image capturing apparatus, the above-described alien substance removing function works at the time of, for example, activation so as to automatically remove alien substances on the surface of the image capturing unit.
Unfortunately, in the image capturing apparatus disclosed in Japanese Patent Application Laid-Open No. 2002-204379, the alien substances adhering to the surface of the image capturing unit absorbs moisture if, for example, the humidity around the image capturing unit is high or if dew condenses on the surface of the image capturing unit. As a result, the adhesion strength of the alien substances to the image capturing unit increases. This sometimes makes it very difficult to remove the alien substances even by executing an alien substance removal operation.
Still worse, even though the alien substances cannot be removed, users may mistakenly consider that the alien substances adhering to the image capturing unit has been properly removed. In this case, the users may start photography even though the alien substances are adhering to the image capturing unit.